The present invention provides a plug for plugging a line and a method for installing a plug in a line.
It is desirable to plug a line for numerous reasons. For instance, if work—such as welding—needs to be carried out on a line, a section may need to be isolated from the other sections of the line (which may be pressurised). Further, a plug may simply be used to seal off a line temporarily.
However, due to the shape of the line, it can be difficult to install such a plug. For instance, it is typically only possible to access one side of a plug (the near side to the user) when installing the plug as the far side of the plug is prevented from being accessed by the installer due to the line and the plug itself being in the way.
One prior art solution is shown schematically in FIGS. 12 and 13. This plug 201 allows the user to install it by accessing only one side of the plug 201 (the left hand side in FIGS. 12 and 13). The plug 201 comprises a first end assembly 210 and a second end assembly 240. Between the first and second end assemblies is a seal 202. The first end assembly 210 comprises a gripping member 216 between two gripping member actuators 270 and 270′. The gripping member 216 is deformable such that when the gripping member actuators 270 and 270′ are moved toward each other, the radius of the gripping member expands (as can be seen in FIG. 13). The seal 202 is deformable such that when the first end assembly 210 and the second end assembly 240 are brought towards each other the radius of the seal expands (as can be seen in FIG. 13). The gripping member actuators 270, 270′ and the second end assembly 240 are made from metal.
The second end assembly 240 is rigidly connected to a threaded axial shaft 280 that passes through the plug 201 to the second end assembly. The first end assembly 210 is slidably mounted on the shaft 280 and is contacted by threaded nut 290, which is threaded onto the shaft 280.
In order for the plug 201 to plug a line, it is necessary for it to be inserted into the line in a relaxed state (the state shown in FIG. 12). It is then necessary to expand the seal 202 and the gripping member 216 radially. This is done by rotating the nut 290 whilst holding the shaft 280 stationary. As can be appreciated, this will bring the gripping member actuator 270 toward gripping member actuator 270′ and will bring the first end assembly 210 toward to the second end assembly 240. This causes the gripping member 216 and the seal 202 to expand simultaneously. Thus, the gripping member 216 can grip the inside of a line and the seal 202 can seal against the inside of the line.
Examples of plugs similar to that shown in FIGS. 12 and 13 have been developed by IK (the HP Plug) and by iNPIPE PRODUCTS (the High Pressure Pipe Plug).
However, the plug of FIGS. 12 and 13 is not an optimal solution for plugging a line. As can be appreciated, the prior art plug 201 requires the installer to apply a torque to one component (such as the nut 290) whilst the installer also holds another component against rotation (such as the shaft 280). Doing so requires special tools and techniques, and increases the complexity of the plug itself. It is therefore desirable to produce a simpler plug, which is easier to install.